Chapter 90:16Non-Melacha Prohibitions

16. If a person sees that he will suffer a loss, for example, one of his
barrels of wine is leaking, he is permitted to ask a Gentile to come over,
even though he knows that the Gentile will mend it. This is allowed even
when the performance of an absolute melacha (Biblical prohibition), is
involved, provided that the Jew does not instruct him, even by allusion, to
fix it. However, it is permitted to say, in his presence (1): "Whoever
will prevent me from suffering this loss will not go unrewarded." This,
however, should only be said when a substantial loss is involved (2).

FOOTNOTES:

(1) One may not address this statement to him directly, for example, by
saying: "if you prevent this loss, you will be rewarded" (Mishna Berura
307:70).

(2) It seems that the Mishna Berura would permit saying it even when the
loss is not substantial (See Mishna Berura 307:71).